/* ----------------------------------------------------------------------
* Copyright (C) 2010 ARM Limited. All rights reserved.
*
* $Date:        15. February 2012
* $Revision: 	V1.1.0
*
* Project: 	    CMSIS DSP Library
* Title:	    arm_fir_sparse_q31.c
*
* Description:	Q31 sparse FIR filter processing function.
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Version 1.1.0 2012/02/15
*    Updated with more optimizations, bug fixes and minor API changes.
*
* Version 1.0.10 2011/7/15
*    Big Endian support added and Merged M0 and M3/M4 Source code.
*
* Version 1.0.3 2010/11/29
*    Re-organized the CMSIS folders and updated documentation.
*
* Version 1.0.2 2010/11/11
*    Documentation updated.
*
* Version 1.0.1 2010/10/05
*    Production release and review comments incorporated.
*
* Version 1.0.0 2010/09/20
*    Production release and review comments incorporated
*
* Version 0.0.7  2010/06/10
*    Misra-C changes done
* ------------------------------------------------------------------- */
#include "arm_math.h"


/**
 * @addtogroup FIR_Sparse
 * @{
 */

/**
 * @brief Processing function for the Q31 sparse FIR filter.
 * @param[in]  *S          points to an instance of the Q31 sparse FIR structure.
 * @param[in]  *pSrc       points to the block of input data.
 * @param[out] *pDst       points to the block of output data
 * @param[in]  *pScratchIn points to a temporary buffer of size blockSize.
 * @param[in]  blockSize   number of input samples to process per call.
 * @return none.
 *
 * <b>Scaling and Overflow Behavior:</b>
 * \par
 * The function is implemented using an internal 32-bit accumulator.
 * The 1.31 x 1.31 multiplications are truncated to 2.30 format.
 * This leads to loss of precision on the intermediate multiplications and provides only a single guard bit.
 * If the accumulator result overflows, it wraps around rather than saturate.
 * In order to avoid overflows the input signal or coefficients must be scaled down by log2(numTaps) bits.
 */

void arm_fir_sparse_q31(
    arm_fir_sparse_instance_q31* S,
    q31_t* pSrc,
    q31_t* pDst,
    q31_t* pScratchIn,
    uint32_t blockSize)
{

	q31_t* pState = S->pState;                     /* State pointer */
	q31_t* pCoeffs = S->pCoeffs;                   /* Coefficient pointer */
	q31_t* px;                                     /* Scratch buffer pointer */
	q31_t* py = pState;                            /* Temporary pointers for state buffer */
	q31_t* pb = pScratchIn;                        /* Temporary pointers for scratch buffer */
	q31_t* pOut;                                   /* Destination pointer */
	q63_t out;                                     /* Temporary output variable */
	int32_t* pTapDelay = S->pTapDelay;             /* Pointer to the array containing offset of the non-zero tap values. */
	uint32_t delaySize = S->maxDelay + blockSize;  /* state length */
	uint16_t numTaps = S->numTaps;                 /* Filter order */
	int32_t readIndex;                             /* Read index of the state buffer */
	uint32_t tapCnt, blkCnt;                       /* loop counters */
	q31_t coeff = *pCoeffs++;                      /* Read the first coefficient value */
	q31_t in;


	/* BlockSize of Input samples are copied into the state buffer */
	/* StateIndex points to the starting position to write in the state buffer */
	arm_circularWrite_f32((int32_t*) py, delaySize, &S->stateIndex, 1,
	                      (int32_t*) pSrc, 1, blockSize);

	/* Read Index, from where the state buffer should be read, is calculated. */
	readIndex = (int32_t)(S->stateIndex - blockSize) - *pTapDelay++;

	/* Wraparound of readIndex */
	if(readIndex < 0) {
		readIndex += (int32_t) delaySize;
	}

	/* Working pointer for state buffer is updated */
	py = pState;

	/* blockSize samples are read from the state buffer */
	arm_circularRead_f32((int32_t*) py, delaySize, &readIndex, 1,
	                     (int32_t*) pb, (int32_t*) pb, blockSize, 1,
	                     blockSize);

	/* Working pointer for the scratch buffer of state values */
	px = pb;

	/* Working pointer for scratch buffer of output values */
	pOut = pDst;


#ifndef ARM_MATH_CM0

	/* Run the below code for Cortex-M4 and Cortex-M3 */

	/* Loop over the blockSize. Unroll by a factor of 4.
	 * Compute 4 Multiplications at a time. */
	blkCnt = blockSize >> 2;

	while(blkCnt > 0u) {
		/* Perform Multiplications and store in the destination buffer */
		*pOut++ = (q31_t)(((q63_t) * px++ * coeff) >> 32);
		*pOut++ = (q31_t)(((q63_t) * px++ * coeff) >> 32);
		*pOut++ = (q31_t)(((q63_t) * px++ * coeff) >> 32);
		*pOut++ = (q31_t)(((q63_t) * px++ * coeff) >> 32);

		/* Decrement the loop counter */
		blkCnt--;
	}

	/* If the blockSize is not a multiple of 4,
	 * compute the remaining samples */
	blkCnt = blockSize % 0x4u;

	while(blkCnt > 0u) {
		/* Perform Multiplications and store in the destination buffer */
		*pOut++ = (q31_t)(((q63_t) * px++ * coeff) >> 32);

		/* Decrement the loop counter */
		blkCnt--;
	}

	/* Load the coefficient value and
	 * increment the coefficient buffer for the next set of state values */
	coeff = *pCoeffs++;

	/* Read Index, from where the state buffer should be read, is calculated. */
	readIndex = (int32_t)(S->stateIndex - blockSize) - *pTapDelay++;

	/* Wraparound of readIndex */
	if(readIndex < 0) {
		readIndex += (int32_t) delaySize;
	}

	/* Loop over the number of taps. */
	tapCnt = (uint32_t) numTaps - 1u;

	while(tapCnt > 0u) {
		/* Working pointer for state buffer is updated */
		py = pState;

		/* blockSize samples are read from the state buffer */
		arm_circularRead_f32((int32_t*) py, delaySize, &readIndex, 1,
		                     (int32_t*) pb, (int32_t*) pb, blockSize, 1,
		                     blockSize);

		/* Working pointer for the scratch buffer of state values */
		px = pb;

		/* Working pointer for scratch buffer of output values */
		pOut = pDst;

		/* Loop over the blockSize. Unroll by a factor of 4.
		 * Compute 4 MACS at a time. */
		blkCnt = blockSize >> 2;

		while(blkCnt > 0u) {
			out = *pOut;
			out += ((q63_t) * px++ * coeff) >> 32;
			*pOut++ = (q31_t)(out);

			out = *pOut;
			out += ((q63_t) * px++ * coeff) >> 32;
			*pOut++ = (q31_t)(out);

			out = *pOut;
			out += ((q63_t) * px++ * coeff) >> 32;
			*pOut++ = (q31_t)(out);

			out = *pOut;
			out += ((q63_t) * px++ * coeff) >> 32;
			*pOut++ = (q31_t)(out);

			/* Decrement the loop counter */
			blkCnt--;
		}

		/* If the blockSize is not a multiple of 4,
		 * compute the remaining samples */
		blkCnt = blockSize % 0x4u;

		while(blkCnt > 0u) {
			/* Perform Multiply-Accumulate */
			out = *pOut;
			out += ((q63_t) * px++ * coeff) >> 32;
			*pOut++ = (q31_t)(out);

			/* Decrement the loop counter */
			blkCnt--;
		}

		/* Load the coefficient value and
		 * increment the coefficient buffer for the next set of state values */
		coeff = *pCoeffs++;

		/* Read Index, from where the state buffer should be read, is calculated. */
		readIndex = (int32_t)(S->stateIndex - blockSize) - *pTapDelay++;

		/* Wraparound of readIndex */
		if(readIndex < 0) {
			readIndex += (int32_t) delaySize;
		}

		/* Decrement the tap loop counter */
		tapCnt--;
	}

	/* Working output pointer is updated */
	pOut = pDst;

	/* Output is converted into 1.31 format. */
	/* Loop over the blockSize. Unroll by a factor of 4.
	 * process 4 output samples at a time. */
	blkCnt = blockSize >> 2;

	while(blkCnt > 0u) {
		in = *pOut << 1;
		*pOut++ = in;
		in = *pOut << 1;
		*pOut++ = in;
		in = *pOut << 1;
		*pOut++ = in;
		in = *pOut << 1;
		*pOut++ = in;

		/* Decrement the loop counter */
		blkCnt--;
	}

	/* If the blockSize is not a multiple of 4,
	 * process the remaining output samples */
	blkCnt = blockSize % 0x4u;

	while(blkCnt > 0u) {
		in = *pOut << 1;
		*pOut++ = in;

		/* Decrement the loop counter */
		blkCnt--;
	}

#else

	/* Run the below code for Cortex-M0 */
	blkCnt = blockSize;

	while(blkCnt > 0u) {
		/* Perform Multiplications and store in the destination buffer */
		*pOut++ = (q31_t)(((q63_t) * px++ * coeff) >> 32);

		/* Decrement the loop counter */
		blkCnt--;
	}

	/* Load the coefficient value and
	 * increment the coefficient buffer for the next set of state values */
	coeff = *pCoeffs++;

	/* Read Index, from where the state buffer should be read, is calculated. */
	readIndex = (int32_t)(S->stateIndex - blockSize) - *pTapDelay++;

	/* Wraparound of readIndex */
	if(readIndex < 0) {
		readIndex += (int32_t) delaySize;
	}

	/* Loop over the number of taps. */
	tapCnt = (uint32_t) numTaps - 1u;

	while(tapCnt > 0u) {
		/* Working pointer for state buffer is updated */
		py = pState;

		/* blockSize samples are read from the state buffer */
		arm_circularRead_f32((int32_t*) py, delaySize, &readIndex, 1,
		                     (int32_t*) pb, (int32_t*) pb, blockSize, 1,
		                     blockSize);

		/* Working pointer for the scratch buffer of state values */
		px = pb;

		/* Working pointer for scratch buffer of output values */
		pOut = pDst;

		blkCnt = blockSize;

		while(blkCnt > 0u) {
			/* Perform Multiply-Accumulate */
			out = *pOut;
			out += ((q63_t) * px++ * coeff) >> 32;
			*pOut++ = (q31_t)(out);

			/* Decrement the loop counter */
			blkCnt--;
		}

		/* Load the coefficient value and
		 * increment the coefficient buffer for the next set of state values */
		coeff = *pCoeffs++;

		/* Read Index, from where the state buffer should be read, is calculated. */
		readIndex = (int32_t)(S->stateIndex - blockSize) - *pTapDelay++;

		/* Wraparound of readIndex */
		if(readIndex < 0) {
			readIndex += (int32_t) delaySize;
		}

		/* Decrement the tap loop counter */
		tapCnt--;
	}

	/* Working output pointer is updated */
	pOut = pDst;

	/* Output is converted into 1.31 format. */
	blkCnt = blockSize;

	while(blkCnt > 0u) {
		in = *pOut << 1;
		*pOut++ = in;

		/* Decrement the loop counter */
		blkCnt--;
	}

#endif /*   #ifndef ARM_MATH_CM0 */

}

/**
 * @} end of FIR_Sparse group
 */
